The 13C and 1H n.m.r. spectra of homocubane, norsnoutane and their 9-keto- and 9,9-ethylenedioxy-derivatives, and a novel route to functionalised brendanes
The 13C and 1H n.m.r. spectra of homocubane (pentacyclo[4.3.0.02,5.03,8.04,7]nonane)(5), norsnoutane (pentacyclo[4.3.0.02,4.03,8.05,7]nonane)(12) and their 9-keto- and 9,9-ethylenedioxy-derivatives have been analysed using deuterium labelling. The protons α to the carbonyl or acetal group and the carbon atoms bearing these protons show unusual absorptions. The substituent effects in homocubanes and norbornanes are similar and no significant additional effect is apparent in the cage structure; the effect of the endo-annulated cyclopropane rings in the norsnoutanes is discussed. The hydrochloric acid-catalysed rearrangement of 9,9-ethylenedioxypentacyclo-[4.3.0.02,4.03,8.05,7]nonane (10) gives the brendane derivative, exo-2-chlorotricyclo[4.2.1.03,7]non-4-en-8-one (16).